```cpp
#include<iostream>
using namespace std;
const int MAXN=100005;
int main(){
int L,n,m;
int a[MAXN];
cin>>L>>n>>m;
int l=0,r=L,mid=0,ans=0,s,j;
for(int i=0;i<n;i++) cin>>a[i];
while(l<=r){
mid=(l+r)/2;
j=0;
s=0;
for(int i=0;i<n;i++){
if(a[i]-a[j]<mid) s++;
else j=i;
}
if(s<=m){
ans=mid;
l=mid+1;
}
else r=mid-1;
}
cout<<ans;
return 0;
}
```
by King_Ding @ 2019-01-27 20:21:16